Acting as if they had just discovered reams of opposition research that had lain unnoticed, Donald Trump’s biggest challengers, Texas Sen. Ted Cruz and Florida Sen. Marco Rubio, knocked into the New York billionaire repeatedly, and he responded in kind.

The exchanges descended for long periods into a biting, interrupting, mocking locker-room-style smackdown, the sound of towel snapping replaced by shrieks from the partisan crowd.

The shock of the debate was not that Rubio and Cruz went after Trump, but that it took them until the end of February, after Trump had notched successive victories, to decide to take him on. The reality, however, is that Trump has rarely been hurt by debates, and it was unclear whether the tag team of the two senators was able to damage him meaningfully at this relatively advanced stage of the campaign.

If Hillary Clinton manages by the end of this campaign to dramatically improve her image, she can credit the cable TV networks and the town halls they have aired incessantly for weeks.

Republican presidential candidates have been throwing around accusations of lying and deceitful campaign tactics....

If Hillary Clinton manages by the end of this campaign to dramatically improve her image, she can credit the cable TV networks and the town halls they have aired incessantly for weeks.

Republican presidential candidates have been throwing around accusations of lying and deceitful campaign tactics....

(Cathleen Decker)

The chance of that rests on whether voters have reached the same point of no return as the candidates and have suddenly decided against nominating the celebrity who has won three of the party’s four contests so far.

As far as clarifying an alternative, there was nothing in Thursday’s barrage to suggest any of the men on stage intended to heed the entreaties of party leaders who would like all but one to drop out to boost the odds of defeating Trump by coalescing the opposition.

If anything, the level of vitriol has only increased as the campaign drives into a huge round of contests in a dozen states on Tuesday. Barring a surge by one or more of the other candidates, Trump victories on that day would put him even more firmly in control of a party whose establishment he has flummoxed.

Not used to sustained criticism, Trump initially seemed taken aback by the virulence Thursday. But while he did fight back, he also kept a steady demeanor for much of the debate, at times looking blandly ahead as if ignoring the criticisms.

“This guy’s a choke artist, and this guy’s a liar,” Trump said of Rubio and Cruz, respectively, in one interlude.

The decision by Cruz and Rubio to hammer at Trump came after even Mitt Romney, a representative of the GOP’s mild-mannered wing, blistered the New York billionaire this week, demanding that he release his income taxes.

The irony was profound — Romney, who sought and received Trump’s endorsement in 2012, had dawdled in releasing his taxes when he was that year’s front-runner for the party's nomination. He also complained repeatedly when Nevada Sen. Harry Reid made unsubstantiated accusations about Romney’s taxes, the same sort of assertions that Romney has now made about Trump.

Whether it was Romney’s call that opened the gates or the prospect for Cruz and Rubio of losing their home states next month to Trump, the withering attack began as the debate opened and never ceased.

In 2 hours and 22 minutes of blistering back-and-forth, Trump was criticized on immigration, healthcare, foreign policy, his support for religious freedom, his backing of Planned Parenthood and his past financial support for Democrats. Some of that had been touched lightly upon in past debates — much of the time by the now-departed Jeb Bush, the former Florida governor who served for months as Trump’s main debate foil and punching bag.

New on Thursday was the robust questioning by Cruz and Rubio of Trump’s business record, his taxes, his involvement in a private university and his loyalty to Republican values. The two stood on either side of Trump, giving the exchanges the feel of a three-man boxing match.

Rubio hit Trump for hiring immigrants in the country illegally to build his hotels. He gibed at Trump’s routine promise to build a wall along the nation’s southern border.

“If he builds the wall the way he built Trump Towers, he'll be using illegal immigrant labor to do it,” Rubio said.

Cruz, operating like the litigator he once was, went after Trump’s past statements as if trying to convince a jury — in this case, the GOP base — that his quarry was lying.

“Donald, true or false, you've said the government should pay for everyone's healthcare,” Cruz barked at one point.

“That’s false,” Trump replied.

“You've never said that?” Cruz replied, a Perry Mason glint in his eye. (Trump had said something of the sort in the past, although he now pledges to repeal President Obama’s healthcare plan, as do all of the other candidates.)

Voters watching Thursday might have decided that Trump is not up to the task of being president, that his idiosyncrasies of ideology and temperament are too great. But that would represent a sea change, for Trump’s distinctive candidacy is what got him this far and, in recent contests, has given him more support than Cruz and Rubio combined.

Cruz and Rubio may have come off as more knowledgeable than Trump, not that specificity has ever been one of Trump’s strengths. But viewers also may have seen Rubio as a speed-talking bully — and it takes something to claim that label from Trump. And Cruz, in his effort to flay Trump, may have seemed overly harsh, such as when, to Trump’s firm disapproval, Cruz seemed to support leaving needy people to die on the sidewalk rather than extend healthcare.

Through all the bickering on Thursday, Trump evinced an oddly consistent approach, if one crafted for this campaign. He praised Planned Parenthood, the nemesis of orthodox conservatives, but an organization used by millions of women. He denounced trade deals as soft-headed, a signal of commiseration with blue-collar workers. He expressed more sympathy for the needy than anyone else on stage, even as he continued to insist that immigrants here illegally be sent back. He seemed to suggest that many things were up for negotiation; the goal was to move ahead.

In all that, he was aiming squarely at the Trump electorate, the economically disaffected and fearful who don’t mind government programs as long as they benefit and want to reclaim a belief that good lies ahead. Or, as Trump would put it, that America can be great again.